The present invention relates generally to laser/detector packages, and particularly to laser/detector packages with components that increase the accuracy of positioning components of a laser/detector package.
A prior art laser/detector package is illustrated in FIG. 1. Laser diode 7 and sensitive photo diode 9 (xe2x80x9cSPDxe2x80x9d) are attached to circular attachment plate 1. In particular, laser diode 7 is attached to sub-mount 8, which is attached to header post 6. Also included is cap 4, which has laser light transparent window 5 and is attached to circular attachment plate 1. Attached to cap 4 is window 5. Header post 6, which functions as a heat sink, is provided on the portion of circular attachment plate 1 covered by cap 4. Semiconductor laser chip 7 is coupled to cathode terminal 2 and anode terminal 12 and SPD 9 is coupled to anode terminal 3. Typically, wires 11 connect semiconductor laser chip 7 to cathode terminal 2 and SPD chip 9 to anode terminal 3.
A drawback of prior art laser/detector packages includes the positioning of laser diode 7 on sub-mount 8. In these systems, the sub-mount is positioned by reference to the top of header post 6. However, header posts 6 are not manufactured with enough accuracy to reliably ensure that laser diode 7, which is mounted on sub-mount 8, is a proper distance from circular attachment plate 1.
Additionally, a reflow sub-process included in various stages of the manufacturing process often causes laser diode 7 and sub-mount 8 to move from their initial position. The reflow sub-process includes placing a laser/detector package in a furnace to reflow solder used to bind laser diode 7 to sub-mount 8 and sub-mount 8 to header plate 6.
When laser diode 7 and sub-mount 8 move from their initial position during the reflow sub-process, the laser/detector package is discarded because there is no accurate way to reposition these components.
There is needed in the art therefore a system and method for manufacturing laser/detector packages that enables a more accurate manufacturing process. In particular, a system and method by which precise positioning of laser/detector package components is possible, movement of laser/detector package components during a reflow sub-process is minimized, and laser/detector package components that do move during a reflow sub-process may be accurately repositioned.
One embodiment of the invention is a laser/detector package comprising an attachment plate having a reference surface; a header post that is perpendicular to the reference surface; a spacer that abuts the reference surface when attached to the header post; a sub-mount that abuts the spacer when attached to the header post; and a laser diode attached to the sub-mount.
Additionally, preferred embodiments of the invention include on the spacer a marking that is perpendicular to the reference surface. This marking permits a more precise and easier positioning and repositioning of the sub-mount and laser diode. A line that is an inherent part of the laser diode and also perpendicular to the reference surface is aligned with the marking.
Further, preferred embodiments of the invention include on the sub-mount a marking that is parallel to the reference surface when the sub-mount is attached to header post. When positioning the laser diode on the sub-mount, the laser diode is positioned such that it abuts the marking on the sub-mount.
In another embodiment of the invention, the laser/detector package comprises an attachment plate having a reference surface; a header post that is perpendicular to the reference surface; a sub-mount that abuts the reference surface when attached to the header post; and a laser diode attached to the sub-mount. Instead of including a separate spacer as in the above described embodiment, the size of the sub-mount is increased so that the laser diode is a proper distance from the reference surface when the sub-mount abuts the reference surface.
Further, preferred embodiments of the invention include on the sub-mount a marking that is parallel to the reference surface and a marking that is perpendicular to the reference surface when the sub-mount is attached to header post. The laser diode is positioned on the sub-mount such that an edge of the laser diode abuts the marking parallel to the reference surface and a line on the laser diode aligns with the marking perpendicular to the reference surface.
Another aspect of the invention includes a method of assembling a laser/detector package that comprises attaching a spacer to the header post so that the spacer abuts the reference surface of the attachment plate; attaching a laser diode to the sub-mount so that the laser diode emits laser beams in a direction parallel to the sub-mount; and attaching the sub-mount to the header post so that the sub-mount abuts the spacer.
Additionally, preferred embodiments of the invention include a) marking the spacer so that the spacer includes a mark that is perpendicular to the reference surface and b) positioning the laser diode with reference to the mark.
Further, preferred embodiments of the invention include marking the sub-mount so that the sub-mount includes a mark that is parallel to the reference surface. When positioning the laser diode on the sub-mount, this mark serves as a guideline to ensure that the laser diode is a precise distance from the circular attachment plate.
Another method of assembling a laser/detector package comprises attaching a laser diode to the sub-mount so that the laser diode emits laser beams in a direction parallel to the front surface of the sub-mount and attaching the sub-mount to the header post so that the sub-mount abuts the reference surface of the attachment plate.
Further, preferred embodiments of the invention include marking the sub-mount so that the sub-mount includes a mark that is parallel to the reference surface and a mark that is perpendicular to the reference surface. When positioning the laser diode on the sub-mount, these marks serve as guidelines to ensure precise positioning of the laser diode.